a band of electromagnetic radiation with wavelengths between gamma rays and ultraviolet radiation, produced by the bombardment of a substance (usu. one of the heavy metals) by a stream of electrons moving at great velocity, as in a vacuum tube, capable of penetrating opaque or solid substances, ionizing gases and body tissues through which they pass or, by extended exposure, destroying tissue, and affecting photographic plates and fluorescent screens, used in diagnosis, and treatment of certain organic disorders, esp. of internal structures of the body; x-ray.

(fig.) a deep, probing examination, going beyond what is apparent.